Characterization of tissue alkaline phosphatases and their partial purification by starch-gel electrophoresis

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Abstract
Alkaline phosphatases from human bone, liver, kidney and intestine have been partially purified by starch-gel electrophoresis. These enzymes have also been recovered from solution in blood serum by electrophoresis. The Km values for the alkaline phosphatases have been compared before and after electrophoresis and after recovery of the enzymes from serum, by using a spectro-fluorimetric enzyme assay with B-naphthyl phosphate as substrate. Reproducible Km values can be obtained for the tissue enzymes submitted to electrophoresis, and although the differences in substrate affinity between phosphatases from individual tissues are small, these differences can be demonstrated after electrophoresis. Mean Km values (m[image][long dash]B-naphthyl phosphate) found after electrophoresis were bone, 0.110; liver, 0.067; intestine, 0.090; kidney, 0.013. By combining starch-gel electrophoresis with spectrofluorimetric determination of phosphatase activity, alkaline phosphatases in blood serum can be studied with reduced interference from activators and inhibitors present in the serum.